(a) Field of the Invention
The present invention relates to a plasma display panel and a method for driving the same. More specifically, the present invention relates to a technique for driving an AC discharge plasma display panel.
(b) Description of the Related Art
Generally speaking, a plasma display panel (hereinafter called as xe2x80x9cPDPxe2x80x9d) has several advantages such as thin configuration, little flicker, large contrast, relatively large display area, high display speed and the like. Thus, plasma display panels will be increasingly used for personal computers, workstations, flat television sets and other applications hereinafter.
There are two different types of PDP with respect to a driving scheme thereof. One is a DC discharge type PDP in which electrode conductors are exposed to the plasma ions, and the other is an AC discharge type PDP in which electrode conductors are covered with a dielectric film for insulation from the plasma ions. The AC discharge type PDP includes a memory PDP in which the display cell itself has a memory function using a charge accumulation effect of the dielectric while discharging through the dielectric, and a refreshing PDP that does not utilize the above memory function. Brightness or intensity of the PDP is generally proportional to the number of discharge times, i.e., the number of repetitive frequency of the drive pulses.
FIG. 1 is a cross section showing a typical AC discharge type color PDP. The PDP includes front and rear glass substrates (panels) 10 and 11. Scanning electrodes 12 and common electrodes 13 are formed on the front substrate 10. An insulator layer 15a is formed covering the scanning electrodes 12 and the common electrodes 13 on the front substrate 10. On the insulator layer 15a, a protective layer 16 made of MgO etc. is formed so as to protect the insulator layer 15a from the plasma discharge. On the other hand, data electrodes 19 are formed on the rear substrate 11. Covering the data electrodes 19, an insulator layer 15b is formed on the rear substrate 11. On the insulator layer 15b, a fluorescent film 18 is formed by coating to convert the ultraviolet ray generated by the plasma discharge into visual light.
A discharge space 20 is formed between the front substrate 10 and the rear substrate 11, and discharge gas including a mixture of He, Ne, Ar, Kr, Xe, N2, O2, CO2 and other gases is filled in the discharge space 20. The discharge space 20 is secured by provision of a lattice partition 17, which separates the front substrate 10 from the rear substrate 11, and divides the discharge space 20 into a plurality of display cells arranged in a matrix. The fluorescent film 18 is colored in red, green or blue in each display cell, so as to display a multi-color image.
FIG. 2 is a schematic block diagram of the PDP shown in FIG. 1 for showing the electrode arrangement of the PDP. The electrode arrangement includes pairs of scanning electrode 121-12m, and common electrode 131-13m, as well as data electrodes 191-19n. Scanning electrodes 121-12m and common electrodes 131-13m constitute row electrodes, which are disposed in parallel to one another in the row direction on the front substrate 10. Data electrodes 191-19n constitute column electrodes, which are disposed in the column direction on the rear substrate 11. Display cells 40 are disposed at respective cross points of the row electrodes and the column electrodes. In FIG. 2, display cells 40 are indicated by blocks arranged in a matrix with mxc3x97n elements.
A conventional method for driving the PDP of FIGS. 1 will be described with reference to a timing chart of FIG. 3 showing pulse waveforms applied to the electrodes of the PDP. A single driving period of the PDP includes a preliminary discharge period, a writing discharge period and a sustaining discharge period, which are iterated in this order so as to display a desired image.
In the preliminary discharge period, an erasing pulse 21 is applied to all the scanning electrodes 121-12m simultaneously, to stop the sustaining discharge, thereby allowing all the display cells 40 to enter an erased state. Thereafter, a preliminary discharging pulse 22 is applied to all the common electrodes 131-13m to force all the display cells to emit light by forced preliminary discharge for facilitating the subsequent writing discharge. Subsequently, a preliminary discharge erasing pulse 23 is applied to the scanning electrodes 121-12m for erasing the preliminary discharge of all the display cells. In this description, xe2x80x9cerase or erasingxe2x80x9d means an operation of decreasing or deleting wall charge accumulated on the insulator.
In the writing discharge period, a scanning pulse 24 is applied to a corresponding one of the scanning electrodes 121-12m, with a certain timing period disposed between each two of the adjacent scanning pulses. In synchrony with the timing of the scanning pulses 24, data pulses 27 corresponding to display data are applied to the selected data electrodes 191-19n. Specifically, the data pulses 27 are applied to data electrodes corresponding to the selected display cells, and not applied to data electrodes corresponding to the unselected display cells. In FIG. 3, diagonal line in each rectangular data pulse 27 indicates that presence or absence of the data pulse 27 depends on the data to be written.
In the following selected display cell, to which the data pulse 27 was applied at the timing of the scanning pulse 24, generates writing discharge in the discharge space 20 between the scanning electrode 12 and the data electrode 19. In the selected display cell that generated the writing discharge, positive wall charge is accumulated on the insulator layer 15a adjacent the scanning electrodes 12. At the same time, negative wall charge is also accumulated on the insulator layer 15b adjacent the data electrodes 19.
In the sustaining discharge period, sustaining pulses 25 and are applied to the common electrodes 131-13m and the scanning electrodes 121-12m so as to perform the sustaining discharge for maintaining a desired intensity in the display cells that performed the writing discharge in the writing discharge period. Specifically, a first sustaining discharge is generated by the potential difference between the positive potential generated by the positive wall charge accumulated on the insulator layer 15a and the negative potential of the first negative sustaining pulses 25 applied to the common electrodes 13. After the first sustaining discharge is generated, the positive wall charge is accumulated on the insulator layer 15a at portions adjacent the common electrodes 13, and the negative wall charge is accumulated on the insulator layer 15a at portions adjacent the scanning electrodes 12. Subsequently, the second sustaining pulses 26 is applied to the scanning electrodes 12 to be superimposed on the potential difference generated by the positive wall charge and the negative wall charge, resulting in generation of a second sustaining discharge.
In the subsequent intervals in the sustaining discharge period, the sustaining discharge is consecutively maintained by superimposing (n+1)th sustaining pulses on the potential difference generated by the positive and negative wall charge accumulated by n-th sustaining discharge. By controlling the number of times for sustaining discharge, the brightness of the display can be controlled for each of the selected display cells. Usually, the sustaining pulses 25 and 26 have repetitive a frequency of approximately 100 KHz at most and each individual pulse has a rectangular waveform.
Since the potentials of the sustaining pulses 25 and 26 are adjusted to a level that does not generate discharge by itself, the wall charge does not exist before the application of the first sustaining pulse 25 in the unselected display cells that did not generate the writing discharge. Therefore, even if the first sustaining pulses 25 are applied, the first sustaining discharge is not generated and no subsequent sustaining discharge is generated in the unselected display cells. In this respect, since the wall charge accumulated by the preliminary discharge is erased by the preliminary discharge erasing pulse 23, no sustaining discharge can be triggered in the unselected display cells.
The conventional AC color PDP as described above, however, has a disadvantage in that the sustaining discharge exhibits a low luminescence efficiency in the PDP, thereby raising the total power dissipation of the PDP.
An object of the present invention is to solve the above-mentioned problem, and to provide a PDP and a method for driving the same, in which the luminescence efficiency for the sustaining discharge can be improved to thereby reduce the power dissipation of the PDP.
The present invention provides a method for driving a plasma display panel (PDP) having a plurality of display cells arranged in a matrix and each receiving therein discharge gas, first and second sustaining electrodes extending in a first direction of the matrix of display cells, and a data electrode extending in a second direction perpendicular to the first direction, the method comprising the steps of selectively applying a writing pulse between the first sustaining electrode and the data electrode, and applying a sustaining pulse train between the first sustaining electrode and the second sustaining electrode, the sustaining pulse train having a repetitive frequency f defined as follows;
fxe2x89xa7xcexciV/(xcfx80d2)
wherein xcexci, V and d are an ion mobility of the discharge gas, a peak voltage of the sustaining pulse train and a distance between the first sustaining electrode and the second sustaining electrode, respectively.
The present invention also provides a plasma display panel (PDP) device comprising first and second panels, a plurality of display cells sandwiched between the first panel and the second panel in a matrix and each receiving therein discharge gas, first and second sustaining electrodes disposed in a first direction of the matrix of display cells, and a data electrode disposed in a second direction perpendicular to the first direction, the first sustaining electrode being disposed for each row of the matrix of display cells, the second sustaining electrode being disposed for a plurality of rows of the matrix display cells.
In accordance with the present invention, since the PDP exhibits a higher luminescence efficiency in the sustaining discharge, the power dissipation of the PDP can be reduced.